I am dog sitting my sisters two dogs while she is overseas for the next month.

One of the dogs is a rescued dog, and very timid especially around men (I'm male).

The dog is relatively used to me, he will sit next to me on the couch for instance, and will accept treats from me (it took a long time before he would come near me, not runaway if I came near him, or accept any food I gave him).

I want to get him to respond to my "come" and "sit", to make life easier for both of us.

Ideally I want him to "come" when he's called and to sit up straight and not cower. If he's not in a situation where he can easily escape when he's on the floor and I come near him, he cowers. He used to panic and bark and run away, so I guess this is an improvement, but he's very hard to deal with when he cowers, for instance putting on his harness/lead is a real pain when he's lying on the ground and being unco-operative and floppy.

He learned, sort of accidentally, to jump up onto the couch when his name is called. Even when my sister calls him at my house, he jumps up onto the couch instead of going to her. I guess it's like his "safe place", and he likes being there because we're less intimidating if he's up higher, and even more so when we're also sitting down.

So I'm trying a few things to teach him to come on demand, but I'm not having much success.

1. I sit on the opposite end of the couch to him, and say "come". Sometimes he will come close enough for me to give him a treat.

2. I sit on the ground next to his "bed" and say "come". He has responded to this once or twice and I give him a treat.

3. I sit in different places around the room and say "come", but he never responds to this, just stares at me, sometimes paces on the couch.

4. I sit on the couch when he isn't on it and say "come", and he will come and jump on the couch and I give him a treat. But I think this might be a mistake as it is associating "come" with the couch and not with me.

All of the training guides I've read for teaching your dog to come, say only give them the command when they are guaranteed to come anyway, and don't associate the command with anything negative.

Well, the dog never comes to me on his own and generally avoids me, and the come command itself is inherently negative because he doesn't really want to be near me.

I'm worried that every time I say "come" and he doesn't come, that I'm just decreasing any chance of success.

Also should note, that I have known this dog for a few years, it has stayed with me before for various periods of time, and that when she first got the dog it would constantly bark and growl at me (and still does at most strangers, especially men) and that I'm not expecting miracles.